Quarkonium results in pa & AA: from RHIC to LHC

Transcription

1 International School of Nuclear Physics 38 th course Nuclear matter under extreme conditions relativistic heavy-ion collisions September 2016 Quarkonium results in pa & AA: from RHIC to LHC Roberta Arnaldi INFN Torino

2 International School of Nuclear Physics 38 th course Nuclear matter under extreme conditions relativistic heavy-ion collisions September 2016 Outlook: Selection on results on Charmonium: J/ and (2S) Bottomonium: (1S), (2S), (3S) in p-a, d-a and A-A collisions at RHIC and LHC energies

3 J/ production probability AA: hot matter effects 3 the original idea quarkonium production suppressed via color screening in the QGP sequential melting differences in quarkonium binding energies lead to a sequential melting with increasing temperature T.Matsui and H.Satz, Phys.Lett.B178 (1986) 416 Statistical regeneration (re)combination enhanced quarkonium production through (re)combination during QGP phase or at hadronization Central AA collisions SPS 20 GeV RHIC 200 GeV LHC 2.76TeV LHC 5.02TeV N ccbar /event ~0.2 ~10 ~85 ~115 Sequential melting energy density P. Braun-Muzinger,J. Stachel, PLB 490(2000) 196 R. Thews et al, Phys.Rev.C63:054905(2001)

4 pa: CNM effects 4 Cold nuclear matter effects: might affect quarkonium production on top of hot matter mechanisms nuclear parton shadowing/ color glass condensate energy loss c c in medium break-up investigated in p-a collisions the assessment of the size of these effects is fundamental to interpret quarkonium A-A results Nuclear modification factor J ψ R AA = J ψ Y AA J ψ T AA σ pp Medium effects are quantified comparing the AA quarkonium yield with the pp one, scaled by a geometrical factor (from Glauber model) R AA = 1 no medium effects R AA 1 hot/cold matter effects

5 Quarkonium in HI 5 p-a p-p vacuum reference for A-A and p-a, genuine pp physics program cold nuclear warm/hot matter effects: matter shadowing/cgc, effects? hadronic energy loss resonance gas (comovers), partonic matter hot matter effects: regeneration vs suppression A-A

6 Quarkonium at RHIC & LHC 6 Facility Experiment System s NN (GeV) RHIC LHC PHENIX STAR ALICE ATLAS CMS LHCb Au-Au, Cu-Cu, Cu-Au, U-U 200, 193, 62, 39 p-a, d-au 200 pp Pb-Pb p-pb 5020 (8000) pp 2760, 7000, 8000, Data taking (2016)

7 Quarkonium at RHIC & LHC 7 Facility Experiment System s NN (GeV) RHIC LHC PHENIX STAR ALICE ATLAS CMS LHCb Au-Au, Cu-Cu, Cu-Au, U-U 200, 193, 62, 39 p-a, d-au 200 pp Pb-Pb Quarkonium p-pb production 5020 investigated via collisions: (8000) with ppdifferent beam 2760, species 7000, at various energies 8000, Data taking (2016)

8 p T (GeV/c) Quarkonium at RHIC & LHC Facility Experiment System s NN (GeV) RHIC LHC PHENIX STAR ALICE ATLAS CMS LHCb Au-Au, Cu-Cu, Cu-Au, U-U 200, 193, 62, 39 Data taking p-a, d-au 200 All pp LHC experiments investigate quarkonium production Pb-Pb p-pb 5020 (8000) pp 2760, complementary 7000, results due to 8000, different kinematic coverages (2016) ATLAS J/ CMS ALICE LHCb ALICE y

9 Quarkonium at RHIC & LHC 9 Facility Experiment System s NN (GeV) RHIC LHC PHENIX STAR LHC Run-1 LHC Run-2 ALICE ATLAS CMS LHCb Au-Au, Cu-Cu, Cu-Au, U-U 200, 193, 62, 39 p-a, d-au 200 pp Pb-Pb p-pb 5020 (8000) 2760 pp 2760, , 8000, Data taking (2016)

10 Quarkonium in AA collisions 10

11 J/ suppression at RHIC 11 Stronger J/ suppression at forward-y wrt mid-y in PHENIX STAR PHENIX mid-y forward-y A. Adare et al. (PHENIX) PRC84(2011) Strong centrality and low-p T suppression Qualitative agreements with suppression + recombination models

12 Energy scan at RHIC 12 STAR PHENIX A. Adamczyk et al. (STAR) arxiv: A. Adare et al. (PHENIX) PRC86(2012) R AA suppression visible at all energies No significant energy dependence, including SPS! Qualitative agreements with suppression + recombination models pp reference at 39 & 62.4 GeV needed for quantitative comparison

13 System scan at RHIC 13 Various systems studied: rather similar suppression observed hint for a weaker suppression in U-U in central U-U collisions: PHENIX PHENIX PRC93(2016) ) stronger color screening suppression AuAu ~ 80-85% UU 2) J/ recombination favoured by 25% larger N coll in U-U N J stat ψ ~ N 2 2 c ~ N coll STAR arxiv: STAR Dominant recombination in U-U over suppression? Quantitative conclusions depend on U Woods-Saxon description

14 J/ : LHC Run1 results 14 Evidence of recombination for low p T J/ at LHC Observation validated by the comparison of LHC results with ALICE 1) lower energy experiments PHENIX forward-y ALICE Coll. PLB 734 (2014) 314 J/ suppression vs centrality is stronger in PHENIX/STAR than in ALICE, in spite of the LHC larger energy densities ALICE PHENIX, STAR Roberta Arnaldi International School of Nuclear mid-yphysics September 17 th 2016

15 J/ : LHC Run1 results Evidence of recombination for low p T J/ at LHC 15 ALICE Coll. PLB 734 (2014) 314 Observation validated by the comparison of LHC results with 1) lower energy experiments forward-y PHENIX ALICE weaker suppression at low p T observed by ALICE ALICE STAR Roberta Arnaldi International School of Nuclear mid-y Physics September 17 th 2016

16 J/ : LHC Run1 results 16 Evidence of recombination for low p T J/ at LHC Observation validated by the comparison of LHC results with ALICE 1) lower energy experiments 2) theoretical models models including (re)combination of J/ in QGP or in the hadronic phase provide a reasonable description of ALICE results still rather large theory uncertainties: models will benefit from a precise measurement of cc and CNM effects PHENIX ALICE JHEP 05 (2016) 179

17 J/ : LHC Run1 results 17 Evidence of recombination for low p T J/ at LHC Observation validated by the comparison of LHC results with 1) lower energy experiments 2) theoretical models 3) high p T J/ results suppression stronger at higher s, as expected from QGP dissociation CMS STAR opposite J/ behavior compared to low-p T results negligible re(combination) effects expected at high p T

18 J/ flow 18 If c quarks participate to QGP collective motion, they should acquire elliptic flow J/ from (re)combination should inherit the flow of c quarks STAR, PRL (2013) ALICE, PRL 111(2013) CMS-PAS-HIN ALICE CMS STAR Hint for J/ flow at LHC, contrary to v 2 ~0 observed at RHIC! ALICE: qualitative agreement with transport models including regeneration CMS: path-length dependence of energy loss?

19 J/ results from LHC Run-2 LHC: Pb-Pb s NN =5.02TeV TeV 2.76TeV arxiv:

20 J/ results from LHC Run-2 LHC: Pb-Pb s NN =5.02TeV High statistics Run-2 allows the R AA evaluation in narrow centrality bins TeV 5.02TeV 2.76TeV Similar centrality dependence at the two energies, with an increasing suppression up to N part ~100, followed by a plateau R 5.02TeV is ~15% higher than the one at 2.76TeV, even if within uncertainties arxiv:

21 J/ theory models s NN =2.76TeV s NN =5.02TeV 21 Brackets represents the possible range of variation of the hadronic J/ Comparison of same theory models at the two energies: TM1, TM2 (Du et al, Zhou et al): rate equation of suppression/regeneration in QGP SHM (Andronic et al): J/ produced by stat. hadronization at phase boundary CIM (Ferreiro): suppression by the comoving partonic medium and regeneration Data are compatible with theory models at both energies Still large uncertainties mainly due to the choice of cc

22 Run-2 J/ results 22 Theoretical and experimental uncertainties reduced in the R AA double ratio Centrality dependence of the R AA ratio is rather flat R AA increases with p T, at both energies, as expected in a regeneration scenario Hint for an increase of R AA, at 5.02TeV, in 2<p T <6 GeV/c Also s NN =5.02TeV results support a picture where a combination of J/ suppression and (re)combination occurs in the QGP

23 (2S) in AA collisions (2S) production modified in AA with a strong kinematic dependence 23 CMS ALICE CMS, PRL 113(2014) Du and Rapp arxiv: J ψ ψ(2s) < RAA Fw-y, 3<p T <30GeV/c R AA later (2S) regeneration, when radial flow is stronger, might explain the rise J ψ ψ(2s) Mid-y 6.5<p T <30GeV/c R AA > RAA stronger suppression of (2S) wrt J/ Chen et al. PLB726(2013)725 J ψ ψ(2s) Fw-y, 0<p T <3GeV/c R AA > RAA ALICE trend agrees with transport models and stat. hadronization approach JHEP 05 (2016) 179 Run1 data not precise enough to conclude on (2S) behavior Run2 results eagerly awaited!

24 (ns) production in AA 24 PRL 109, (2012) Main features of bottomonium production wrt charmonium: no B hadron feed-down smaller gluon shadowing effects negligible (re)combination more robust theoretical predictions due to the higher b quark mass with a drawback smaller production cross-section PbPb pp Clear suppression of states in PbPb at LHC energies with respect to pp collisions

25 Run-1 (ns): where we stand? Sequential suppression observed at LHC in Run 1: Υ(3S) Υ(2S) Υ(1S) R AA < RAA < RAA R AA ( (1S))= R AA ( (2S))= R AA ( (3S))< 0.14 at 95% CL centrality dependent suppression for (1S) and (2S) 25 at LHC (1S) is already suppressed in semiperipheral collisions, while at RHIC only in the central ones CMS, PRL109 (2012) and HIN STAR, PLB735 (2014) 127 and preliminary U+U feed-down from excited states + CNM are enough to explain the observed (1S) suppression?

26 LHC Run-1 (ns) results 26 no p T or y dependence of the (1S) and (2S) suppressions models reproduce the p T and centrality dependence rapidity description still needs tuning

27 LHC Run-2 (ns) results TeV 2.76TeV Centrality dependent (1S) R AA suppression observed also at s NN =5.02TeV No firm conclusion on the R AA energy dependence within the current uncertainties

28 (ns) theory models 28 Theory models, with (Emerick et al.) or without (Zhou et al.) regeneration component, qualitatively reproduce the data within uncertainties Different trend in data and theory for most forward-y?

29 (ns) at RHIC 29 (1S) is also suppressed at RHIC, in central collisions, even if less wrt LHC R AA ( (1S))= (AuAu+UU) STAR: excited states accessible in the muon channel arxiv: Hint of less suppression of excited states wrt LHC

30 Quarkonium in p-a collisions 30

31 pa J/ results at LHC 31 J/ affected by CNM effects, with a strong y and p T dependence: R pa decreases towards forward y data consistent with shadowing and coherent parton energy loss models agreement with CGC depends on implementation JHEP 02(2014)073, JHEP 06(2015)055 good agreement between ALICE and LHCb (similar kinematic range) different behavior at mid-y for low and high p T J. JHEP 02 (2014) 072 JHEP 02(2014)072

32 transv. momentum centrality J/ vs pt and centrality backward-y mid-y forward-y 32 mid and fw-y: suppression increases vs centrality and is larger at low p T backward-y: hint for increasing Q pa vs centrality, with rather flat p T trend Shadowing and coherent energy loss models in fair agreement with data

33 From pa to AA 33 Once CNM effects are measured in ppb, what can we learn on J/ production in PbPb? Hypothesis: 2 1 kinematics for J/ production CNM effects (dominated by shadowing) factorize in p-a CNM obtained as R pa x R Ap, similar x-coverage as PbPb we get rid of CNM effects with AA / pa x Ap ppb x Pbp PbPb CNM effects not enough to explain PbPb data at high p T Pb-Pb p-pb Evidence for hot matter effects in Pb-Pb!

34 (2S) production in pa, da 34 (2S) suppression is stronger than the J/ one, both at RHIC and LHC unexpected since time spent by the cc in the nucleus ( c ) is shorter than charmonium formation time ( f ) shadowing and energy loss, almost identical for J/ and (2S), do not account for the different suppression Only models including QGP + hadron resonance gas or comovers describe the stronger (2S) suppression ALICE, JHEP 1606(2016)050

35 (1s) in pa collisions 35 No significant rapidity dependence of (1S) R pa (ALICE and LHCb agree within uncertainties) Shadowing and energy loss models are compatible at forward-y At backward-y smaller antishadowing is suggested ALICE, Phys. Lett. B 740 (2015) 105 ATLAS-CONF ,LHCb, JHEP 07(2014)094

36 excited states in pa 36 p-pb vs Stronger excited states suppression with respect to (1S) Initial state effects similar for the three states Final states effects in p-pb? CMS,JHEP04(2014)103 p-pb vs : even stronger suppression of excited states in PbPb ALICE (and LHCb) observes: (2S)/ (1S) (ALICE) CMS 2.03<y<3.53: HIN , JHEP ±0.08±0.04 (2014) 103, PRL 109 (2012) -4.46<y<-2.96: 0.26±0.09±0.04 compatible with pp results 0.26 ± 0.08 (ALICE, pp@7tev) Rapidity dependent final state effects at play?

37 RHIC and LHC Prospects 37 sphenix (>2020) Precision spettroscopy (80MeV resolution expected) LHC heavy-ion program 2016: pa at s NN = 5.02 and 8 TeV 2018: PbPb : LHC Run3 L int > 10nb -1 for PbPb (is ~1nb -1 in Run2) : LHC Run4 LHCb Joined the PbPb data taking in 2015: covers peripheral semi-periph. Range SMOG: fixed target pa program at LHC, up to s =110 GeV

38 Conclusions 38 A large sample of quarkonium results in various systems and at various energies is now available from both RHIC and LHC! A combination of suppression and regeneration mechanisms affects J/ production at RHIC and LHC Theory models qualitatively describe the data, but still large uncertainties (open charm cross section) CNM effects (mainly shadowing and energy loss) play an important role, as observed in pa collisions Bottomonium results might be compatible with sequential suppression in QGP Thanks!

39 Conclusions 38 A large sample of quarkonium results in various systems and at various energies is now available from both RHIC and LHC! J/ suppression at RHIC and LHC is interpreted as a combination of suppression and regeneration mechanisms Theory models qualitatively describe the data, but still large uncertainties (open charm cross section) CNM effects (mainly shadowing and energy loss) play an important role, as observed in pa collisions Bottomonium results might be compatible with sequential suppression in QGP Thanks!

40 Backup slides 40

41 AA: from suppression the original idea: quarkonium production suppressed via color screening in the QGP 41 sequential melting differences in the quarkonium binding energies lead to a sequential melting with increasing temperature (2S) J/ (1S) T c PHENIX, Phys.Rev C91, Quarkonium as QGP thermometer T>>T c Roberta Arnaldi CONF12 August 30 th 2016

42 Evolution of J/ <p T2 > 42 ALICE,arXiv: r AA = p T 2 AA p T 2 pp r AA centrality evolution strongly depends on s decreasing r AA trend, observed at LHC due to (re)combination, which dominates J/ production at low p T TM1: Zhao et al., Nucl.Phys.A859 (2011) 114 TM2: Zhou et al. Phys.Rev.C89 (2014) transport models, already describing J/ R AA, also reproduce the r AA evolution Roberta Arnaldi CONF12 August 30 th 2016

43 J/ at very low p T Strong R AA enhancement in peripheral collisions for 0<p T <0.3 GeV/c 43 significance of the excess is 5.4 (3.4) in 70-90% (50-70%) behaviour not predicted by transport models excess might be due to coherent J/ photoproduction in PbPb (as measured also in UPC) if excess is removed requiring p T J ψ >0.3GeV/c ALICE R AA lowers by 20% at maximum (in the most peripheral bin) Roberta Arnaldi CONF12 August 30 th 2016

44 2.76TeV RAA vs pt 44 ALICE, PLB 734 (2014) 314, JHEP 07(2015)051, arxiv: TeV PHENIX Rapp Zhuang PHENIX Roberta Arnaldi CONF12 August 30 th 2016

45 Multi-differential J/ studies45 p T -centrality multi-differential studies allows detailed comparison with theory models 0-20% 20-40% 40-90% Zhao et al., Nucl.Phys.A859 (2011) 114 Zhou et al. Phys.Rev.C89 (2014) ALICE, arxiv: Model provide a fair description of the data, even if with different balance of primordial/regeneration components Still rather large theory uncertainties: models will benefit from precise measurement of cc and CNM effects Roberta Arnaldi CONF12 August 30 th 2016

46 LHC Run-2 J/ results 46 Roberta Arnaldi CONF12 August 30 th 2016

47 (2S) production in pa 47 Being more weakly bound than the J/, the (2S) is an interesting probe to have further insight on the charmonium behaviour in pa Low energy (2S) p-a results from NA50, E866 and HERA-B: mid-y (x F ~0): (2S) suppression stronger than J/ one, interpreted via pair break-up fully formed resonances traversing the nucleus E866 Collab., PRL 84 (2000) 3256 c c (2S) charmonium formation time<crossing time forward-y (high x F ): suppression becomes identical dominated by energy loss c c (2S) charmonium formation time>crossing time x F Roberta Arnaldi CONF12 August 30 th 2016

48 (2S) versus crossing time 48 c = L β z γ D. McGlinchey, A. Frawley and R.Vogt, PRC 87, (2013) Forward-y: c << f interaction with nuclear matter cannot play a role c c (2S) Backward-y: c f indication of effects related to break-up in the nucleus? c c (2S) Roberta Arnaldi CONF12 August 30 th 2016

49 (2S) / J/ double ratio 49 Similar suppression trend observed versus centrality, by both ALICE and PHENIX QGP+hadron resonance gas (Rapp) or comovers models (Ferreiro) describe the observed suppression Roberta Arnaldi CONF12 August 30 th 2016

50 Y vs ev. activity 50 CMS 50

51 Y compared to theory 51

52 J/ production at RHIC 52 (re)combination/suppression role investigated comparing U-U and AuAu in central U-U collisions: 1) stronger suppression due to color screening AuAu ~ 80-85% UU N coll scaling 2 N coll scaling 2) J/ recombination favoured by 25% larger N coll in UU 2 N J ψ stat ~ N c 2 ~ N coll 2 results slightly favour N coll scaling dominant (re)combination over suppression when going from central U-U to Au-Au collisions quantitative comparison depends on the choice of the uranium Woods-Saxon parametrizations PHENIX, arxiv: Roberta Arnaldi Quark Matter 2015 October 2 nd 2015

53 STAR CMS CMS-PAS-HIN

54 (2S) production in pa 54 (2S) suppression is stronger than the J/ one, both at RHIC and LHC unexpected since time spent by the cc in the nucleus ( c ) is shorter than charmonium formation time ( f ) shadowing and energy loss, almost identical for J/ and (2S), do not account for the different suppression Only models including QGP + hadron resonance gas or comovers describe the stronger (2S) suppression ALICE, JHEP 1606(2016)050

55 Comparison to theoretical models 55 QGP+hadron resonance gas (Rapp) or comovers models (Ferreiro) reasonably describe both J/ and (2S) suppression at RHIC and LHC pa RHIC pa LHC dau RHIC Ferreiro, PLB 749(2015)98 dau RHIC Du et al. arxiv:

56 CNM effects at RHIC 56 Disentangling CNM mechanisms is challenging shadowing + cc break-up describe R dau vs y, but meets some difficulties for R dau vs p T coherent energy loss contribution induces a less flat R dau dependence on p T -2.2<y<-1.2 Arleo et al. JHEP1305 (2013) 155

57 CNM effects at RHIC 57 Comparison between heavy flavor and quarkonium: d+au 200 GeV R da of HF muon and J/ψ are consistent at forward rapidity, but clearly different at backward rapidity charm production is enhanced but J/ψ production is significantly suppressed due to nuclear breakup inside dense comovers at backward rapidity Contrarily to LHC, at RHIC energies a contribution from J/ breakup in nuclear matter could be present ( J/ -N ~ 4mb) PHENIX: PRC PHENIX: PRL